It would be great if there was some sort of way of alerting you whether you are going to be overwriting a file that's already been uploaded to dropbox, through the web client.
For example, I am uploading a batch of very large psd's but half of them have already been uploaded previously, it would be convenient if there was some sort of prompt asking if I would like to re-write the files already in existence or skip replacing those and only upload whatever isn't already there, that way I don't have to re-upload the full set of files. Similar to how the desktop client would work when you're using it from whatever operating system you're on.